Conventionally, a metal vapor discharge lamp that has characteristics of high intensity, high efficiency, and a long life, such as a metal halide lamp is widely used in various places because of the above characteristics. Recently, a low-power-consumption metal halide lamp which is compact and has high color rendering properties has been developed, and such a metal halide lamp is used as, for example, a light source of an illumination apparatus (a so-called spotlight) which illuminates articles on display such as a commercial product or the like in a spot manner.
A conventional illumination apparatus includes, in addition to the above metal halide lamp, a reflector having a concave reflecting surface to reflect light emitted from the metal halide lamp in a desired direction. As the reflector, a so-called closed-type reflector is typically used, which has an opening (light extracting part) closed with, for example, a front glass plate. This is because of the following reason. If the metal halide lamp that does not take explosion-proof measures is damaged by some reasons, a fragment of the damaged metal halide lamp is prevented from scattering to outside of the reflector.
On the other hand, because the metal halide lamp has high intensity, if direct light emitted from the metal halide lamp enters human eyes, glare is caused. Therefore, concavo-convex processing for diffusing light is performed on the front glass plate, or a glare cap for shielding light emitted from the metal halide lamp is provided on the front glass plate, for example (such as a patent document 1).
Patent Document 1: Japanese Published Patent Application No. H11-96973